Insight into Glyproline Peptides' Activity through the Modulation of the Inflammatory and Neurosignaling Genetic Response Following Cerebral Ischemia-Reperfusion

Glyprolines are Gly-Pro (GP)- or Pro-Gly (PG)-containing biogenic peptides. These peptides can act as neutrophil chemoattractants, or atheroprotective, anticoagulant, and neuroprotective agents. The Pro-Gly-Pro (PGP) tripeptide is an active factor of resistance to the biodegradation of peptide drugs. The synthetic Semax peptide, which includes Met-Glu-His-Phe (MEHF) fragments of adrenocorticotropic hormone and the C-terminal tripeptide PGP, serves as a neuroprotective drug for the treatment of ischemic stroke. Previously, we revealed that Semax mostly prevented the disruption of the gene expression pattern 24 h after a transient middle cerebral artery occlusion (tMCAO) in a rat brain model. The genes of this pattern were grouped into an inflammatory cluster (IC) and a neurotransmitter cluster (NC). Here, using real-time RT-PCR, the effect of other PGP-containing peptides, PGP and Pro-Gly-Pro-Leu (PGPL), on the expression of a number of genes in the IC and NC was studied 24 h after tMCAO. Both the PGP and PGPL peptides showed Semax-unlike effects, predominantly without changing gene expression 24 h after tMCAO. Moreover, there were IC genes (iL1b, iL6, and Socs3) for PGP, as well as IC (iL6, Ccl3, Socs3, and Fos) and NC genes (Cplx2, Neurod6, and Ptk2b) for PGPL, that significantly changed in expression levels after peptide administration compared to Semax treatment under tMCAO conditions. Furthermore, gene enrichment analysis was carried out, and a regulatory gene network was constructed. Thus, the spectra of the common and unique effects of the PGP, PGPL, and Semax peptides under ischemia-reperfusion were distinguished.

ACTH(6-9)-Pro-Gly-Pro ameliorates anxiety-like and depressive-like behaviour and gut mucosal microbiota composition in rats under conditions of chronic restraint stress

The effects of the peptide ACTH(6-9)-Pro-Gly-Pro at doses of 5; 50; 500 μg/kg on the Wistar rats' behaviour and gut mucosal microbiota composition under conditions of chronic immobilization stress (CRS) were studied. CRS increased anxiety-like and depressive-like behaviour, disturbances in locomotor activity and gut dysbiosis. Administration of ACTH(6-9)-Pro-Gly-Pro showed many phenotypic results. Peptide demonstrated anti-depressant activity at doses of 5 and 500 μg/kg by a decrease in the total immobile time in the FST. ACTH(6-9)-Pro-Gly-Pro administered at a dose of 50 μg/kg resulted in an anxiolytic effect which is shown by an increase in the time in the open arms of EPM (p < 0.05) and a decrease in the time in the closed arms (p < 0.05). Moreover, the peptide led to a decrease in alpha- and beta-diversity of the gut microbiota (p < 0.01). Correlation and linear regression analysis demonstrated central mechanisms of ACTH(6-9)-Pro-Gly-Pro anxiolytic activity and both central and peripheral ones in an anti-depressant effect. In this way, peptide ACTH(6-9)-Pro-Gly-Pro could prevent the development of behavioural disturbances and gut dysbiosis caused by chronic restraint stress.

ACTH(6-9)PGP Peptide Protects SH-SY5Y Cells from H2O2, tert-Butyl Hydroperoxide, and Cyanide Cytotoxicity via Stimulation of Proliferation and Induction of Prosurvival-Related Genes

Stabilized melanocortin analog peptide ACTH(6-9)PGP (HFRWPGP) possesses a wide range of neuroprotective activities. However, its mechanism of action remains poorly understood. In this paper, we present a study of the proproliferative and cytoprotective activity of the adrenocorticotropic hormone fragment 6-9 (HFRW) linked with the peptide prolyine-glycyl-proline on the SH-SY5Y cells in the model of oxidative stress-related toxicity. The peptide dose-dependently protected cells from H2O2, tert-butyl hydroperoxide, and KCN and demonstrated proproliferative activity. The mechanism of its action was the modulation of proliferation-related NF-κB genes and stimulation of prosurvival NRF2-gene-related pathway, as well as a decrease in apoptosis.

Phosphine modification of proline-glycine-proline tripeptide and study of its neuroprotective properties

BACKGROUND

Treatment of neurodegenerative diseases, such as Parkinson's disease, Huntington's chorea, Alzheimer's disease, is one of the priority directions in modern medicine. Thus, search and production of new physiologically active substances for the treatment of neurodegenerative disorders is one of the most important tasks for organic chemistry. The approach based on the replacement of a peptide bond in a peptide molecule with a structural isostere, non-hydrolyzable methylene phosphoryl fragment makes it possible to increase the metabolic stability of peptide molecules to the destructive action of peptidases.

METHODS

This work is devoted to the approbation of a new synthetic approach to the production of physiologically active substances in a series of peptide-type compounds with activity by replacing the peptide bond with isosteric methylene-phosphoryl fragment with the preservation of the original amino acid sequence.

RESULTS

A phosphine analog of the known physiologically active tripeptide proline-glycine-proline was obtained, cytotoxicity and neuroprotective properties of the initial tripeptide and its phosphine analog were studied.

CONCLUSION

Preliminary biological tests have shown that the obtained phosphine analog of the proline-glycine-proline tripeptide is involved in modulating the formation of sediments in the cellular system of proteinopathy, which may indicate their potential antiaggregatory properties.

[Pharmacokinetics of noopept and its active metabolite cycloprolyl glycine in rats]

The study of the pharmacokinetics of new drugs and the identification of active metabolites is a necessary step for effective and safe use in the clinical practice. It is especially important for peptide drugs due to their enzymatic instability, low bioavailability and poor permeability through the blood-brain barrier (BBB). The role of endogenous neuropeptides containing cyclic amino acids, proline, pyroglutamic acid, and glycine, in the regulation of memory processes is known as terminal peptide fragments. The development of nootropic drugs based on natural neuropeptides with high pharmacological activity and improved pharmacokinetic properties (enzymatic stability, high bioavailability, and good permeability through the BBB) is an important problem of modern neuropsychopharmacology. Developed drugs - representing short (di- and tri-) peptides appear to meet these requirements. In the Zakusov Research Institute of Pharmacology a nootropic agent noopept (N-phenylacetyl-prolyl-L-glycine ethyl ester), was developed and introduced into medical practice, studies of its pharmacokinetics in ratsrevealed that the noopept metabolite found in the rat plasma and brain, cyclo-prolyl-L-glycine (CPG), differed significantly in its pharmacokinetic parameters from noopept, but at the same time it had similar noopept multi-component spectrum of pharmacological action, namely the influence on higher integrative functions of memory.

GABA, Selank, and Olanzapine Affect the Expression of Genes Involved in GABAergic Neurotransmission in IMR-32 Cells

Clinical studies have shown that Selank had an anxiolytic effect comparable to that of classical benzodiazepine drugs, which can enhance the inhibitory effect of GABA by allosteric modulation of GABA_A receptors. These data suggest that the molecular mechanism of the effect of Selank may also be related to its ability to affect the performance of the GABAergic system. To test this hypothesis, we studied the changes in expression of 84 genes involved in the functioning of the GABAergic system and in the processes of neurotransmission in the culture of neuroblastoma IMR-32 cells using qPCR method. As test substances, in addition to Selank, we selected the major GABA_A receptor ligand, GABA, the atypical antipsychotic, olanzapine, and combinations of these compounds (Selank and GABA; Selank and olanzapine). We found no changes in the mRNA levels of the genes studied under the effect of Selank. The combined effect of GABA and Selank led to nearly complete suppression of changes in expression of genes in which mRNA levels changed under the effect of GABA. When Selank was used in conjunction with olanzapine, the expression alterations of more genes were observed compared with olanzapine alone. The data obtained indicate that Selank has no direct effect on the mRNA levels of the GABAergic system genes in neuroblastoma IMR-32 cells. At the same time, our results partially confirm the hypothesis that the peptide may affect the interaction of GABA with GABA_A receptors. Our data also suggest that Selank may enhance the effect of olanzapine on the expression of the genes studied.

Peptide Selank Enhances the Effect of Diazepam in Reducing Anxiety in Unpredictable Chronic Mild Stress Conditions in Rats

It was shown that the anxiolytic effect of Selank is comparable to that of classical benzodiazepine drugs and that the basis of their mechanism of action may be similar. These data suggest that the presence of Selank may change the action of classical benzodiazepine drugs. To test this hypothesis, we evaluated the anxiolytic activity of Selank and diazepam in rats both under conditions of unpredictable chronic mild stress and in its absence, after the individual and combined administration of these compounds using the elevated plus maze test. We found that, even in the absence of chronic stress, the administration of a course of test substances changed anxiety indicators toward their deterioration, but the changes after the administration of a course of Selank were less pronounced. In conditions of chronic stress, anxiety indicator values after the simultaneous use of diazepam and Selank did not differ from the respective values observed before chronic stress exposure. The data obtained indicate that the individual administration of Selank was the most effective in reducing elevated levels of anxiety, induced by the administration of a course of test substances, whereas the combination of diazepam with Selank was the most effective in reducing anxiety in unpredictable chronic mild stress conditions.

Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission

Clinical studies have shown the similarity of the spectrum of physiological effects of Selank and classical benzodiazepines, such as diazepam and phenazepam. These data suggest that there is a similar basis of their mechanism of action. To test this hypothesis we studied the effect of Selank and GABA on the expression of genes involved in neurotransmission. We analyzed the expression of 84 genes involved in neurotransmission (e.g., major subunit of the GABA receptor, transporters, ion channels, dopamine, and serotonin receptors) in the frontal cortex of rats 1 and 3 h after the administration of Selank or GABA (300 μg/kg) using real-time PCR method. We found significant changes in the expression of 45 genes 1 h after the administration of the compounds. Three hours after Selank or GABA administration, 22 genes changed their expression. We found positive correlation between the changes in genes expression within 1 h after administration of Selank or GABA. Our results showed that Selank caused a number of alterations in the expression of genes involved in neurotransmission. The data obtained indicate that Selank is characterized by its complex effects on nerve cells, and one of its possible molecular mechanisms is associated with allosteric modulation of the GABAergic system.

[Proteolysis of simple glyprolines by leucine aminopeptidase and enzymes from nasal slime, brain membranes, and rat blood]

Proteolysis of Pro-Gly-Pro-Leu, Pro-Gly-Pro-Gly and Pro-Gly-Pro were studied comparatively to Met-Glu-His-Phe-Pro-Gly-Pro (semax). It is shown that all three peptides are considerably more stable to proteolysis by N-leucine-aminopeptidase (EC 3.4.11.1, Sigma, type VI, 9.2 units/mg), and by enzymes of nasal slime, brain microsomal fractions, and rat blood. Metabolites of the proteolysis showed that semax derives His-Phe-Pro-Gly-Pro only, Pro-Gly-Pro-Leu forms Gly-Pro-Leu, Pro-Gly-Pro and Gly-Pro, Pro-Gly-Pro-Gly gives Pro-Gly-Pro and Gly-Pro, and Pro-Gly-Pro forms Gly-Pro.